The components of high-temperature mechanical systems, such as, for example, gas-turbine engines, must operate in severe environments. For example, the high-pressure turbine blades, vanes, blade tracks, and blade shrouds are exposed directly to hot flow path gases in commercial aeronautical engines and typically experience metal surface temperatures of about 800° C., with short-term peaks as high as 1100° C. The rim portion of a turbine disk may experience high temperatures of between approximately 600° C. and 750° C.
On the other hand, the hub portion of the turbine disk may not be exposed to such high temperatures, but may experience higher mechanical stresses. Thus, it may be desired for the hub portion of the turbine disk to possess different mechanical properties than the rim portion of the turbine disk.
One technique of providing different mechanical properties to two portions of a single component is to process the component in such a way that a grain size in one portion of the component is different than the grain size in a second portion of the article.